It is suggested in the art that surface activated silica particles having grafted polymers on the surface thereof may be useful in chromatography and for adsorbing a variety of organic compounds from water. However, heretofore it was thought by those skilled in the art that incomplete coverage by the surface activating compound on the silica particles was very beneficial to insure wetting and to graft polymerize a water soluble polymer onto the surface of said silica particles. See, for example, "Study of the Chemistry of the Surface of An Adsorbent Based on Silokhrom and N-Vinylpyrrolidone", Zubakova et al., Zhurnal Prikladonoi Khimii, vol. 60, 1491-1494 (1987). In this article, the authors state that when using acetone as a solvent they obtain a surface coverage on the silica of 2 micromoles of vinyl triethoxysilane per square meter of silica. After the surface activating step the author then state that they graft polymerize polyvinylpyrrolidone onto the silica in order to obtain 1.6 milligrams of polyvinylpyrrolidone per square meter of silica.
The present invention differs substantially from that of the Zubakova et al. article in that in the present invention a vinyl lower alkoxy silane is chemically bonded to silica particles using a lower alkyl benzene as a solvent for the vinyl loweralkoxy silane to obtain a surface coverage on the silica of at least 10 micromoles of the vinyl loweralkoxy silane per square meter of silica particles. The lower alkoxy moieties are then hydrolyzed to hydroxyl groups. I have found that even with having the silane compound cover such a large surface area that wetting is ideal and that graft polymerization of the surface activated silica particle is enhanced when utilizing a water soluble vinyl polymer. In fact, I have found that when I graft polymerize thereon a water soluble vinyl polymer, I obtain at least about 2.5 milligrams of said water soluble polymer per square meter of said silica particles. This was truly surprising and unexpected.
A subsequent paper by Krasilmikov, et al. entitled "Adsorption and Chromatographic Properties of Modified Silica Sorbents for the Production of Viral Preparations"Journal of Chromatography, 446, 211-219 (1988), states that preparing silica resins using the process of Zubakova, et al., produces a solid separation resin useful in purifying viruses. The amount of polyvinylpyrrolidone attached to the surface of the silica particles is not mentioned by the author. In view of the fact that they used the same method as described by Zubakova, et al., the amount of polyvinylpyrrolidone cannot have exceeded 1.6 mg/m.sup.2.
A paper by Korshak, et al., entitled "Chemical Grafting of Vinyl Heterocyclic Monomers to the Surface of Mineral Carriers", Vysokomol. Soyed, A21:No. 5, 1132-1138 (1979) disclose s a method for chemical grafting of polyvinylpyrrolidone onto silica particles surface activated with vinyl trichloro silane.
The author reports that the highest amount of grafted vinyl groups onto the surface of the silica particles was only 4.4 micromoles of vinyl trichloro silane per square meter of silica particles. On page 1250 of the article, the author further report that the grafting of polyvinylpyrrolidone on the surface activated silica particles resulted in a yield of only about 1.1 mg/m.sup.2 which, coincidentally, is about the amount of polymer that can be physically adsorbed.
The three articles cited above provide, to those skilled in the art, very sketchy information and none of the articles disclose or suggest that the author actually grafted more polymer onto the silica particles than could be physically adsorbed from the reaction mixture.
In contrast, in my invention, the amount of chemically grafted vinyl water soluble polymer is much higher than the amount that can be physically bonded and my separation resins are very useful in the separation of higher molecular weight organic compounds from aqueous systems as well as adsorbing chemical compounds which are attracted to the grafted vinyl water soluble polymer from aqueous systems.